The Large Hadron Collider (LHC) at the European Laboratory for Particle Physics (CERN, Switzerland) recently reached an important milestone on its way to probing our understanding of the beginning and nature of our universe. Since last year this unique machine provides interactions of protons at unprecedented collision energies. The first collisions at 7 TeV took place.

Dr Andre Mischke, based at Universiteit Utrecht and holder of an ERC Starting Grant (*),was then in charge as the Period Run Coordinator of the ALICE Collaboration, guaranteeing the proper running of the complex ALICE detector and serving as the contact person to the LHC machine experts. He spent the night before the 30 March in the LHC main control room.

The unprecedented energy threshold achieved takes us ten millionths of a second close to the Big Bang, at an equivalent temperature of 10^12 Kelvin, which is a hundred thousand times hotter than the Sun’s core. In those conditions matter exists in a state never seen before, only described by the theoretical predictions of the so-called Standard Model of particle physics.

This novel state of matter can be created and studied in the laboratory by colliding atomic nuclei at very high energies in particle accelerators. There the most intimate components of nucleons in the atomic nucleus, the quarks, can exist unconfined and intermingled with the mediators of the nuclear strong interaction, the gluons.
At that very high energy quarks can recombine into states not allowed in ordinary matter. One of those states is the D* meson, spotted for the first time in the ALICE detector at LHC in the past weeks. This primordial "soup", the "quark-gluon plasma", quickly expands and cools down, until it passes the phase boundary, where it transforms back to "ordinary matter" like in the very early universe, but on a small scale and for a much shorter time.
The observations gained beyond this landmark reached by LHC will tell us the way to the correct physics beyond the Standard Model. Correlations of heavy-quark particles (such as the D* mesons) can serve as a sensitive probe to study the dynamical properties of the quark-gluon plasma.

According to Dr Mischke, his group "achieved the first observation of the signal of an exotic particle at the highest collision energy ever reached using the ALICE detector. We got a first glance of what we can expect in this new regime of physics in the next years".

(*) ERC-2007-StG 210223 QGP, Characterisation of a novel state of matter: The Quark-Gluon Plasma, funded with 850,000 Euro over five years.

http://public.web.cern.ch/public/en/LHC/ALICE-en.html

A proton-proton interaction in ALICE at a collision energy of 7 TeV taken

Scientists see the first 7 TeV particle collisions in the control room